Abstract
Battery management systems (BMSs) are key components in battery storage systems in order to guarantee their safe operation and improve their performance, reliability, and efficiency. BMSs monitor critical parameters in the battery as state of charge (SOC), state of health (SOH), or temperature. Direct measure of SOC or SOH is not possible, while temperature, on the other hand, can be measured with different types of sensors. These sensors, although cost-effective, raise concerns regarding cabling, signal conditioning and acquisition systems, increasing cost, complexity, and decreasing reliability. The internal resistor of the battery has already been successfully used to estimate these parameters. BMS can also include the function of balancing (equalizing) cells of a battery pack. Among all available equalizing systems, those based on switched capacitors are interesting due to their simplicity and easy scalability. This article proposes an internal resistance (IR) estimation method for LiFePO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> batteries using signals naturally produced by a switched-capacitor equalizer (SCE). The IR will be used to estimate the battery temperature. It will be shown that the method can operate online and without interfering with the regular operation of the SCE.
Highlights
The use of battery-based Energy Storage Systems (ESS) has highly increased in the last decades [2]
It must be noted that the proposed method estimates the internal resistance (IR), Ri in Fig. 8, which is dominated by the metal collectors and leads [27], which resistances increase as temperature does [11], [15]
EXPERIMENTAL RESULTS The switched capacitor equalizer (SCE) shown in Fig. 1c was used to carry out the experimental results
Summary
The use of battery-based Energy Storage Systems (ESS) has highly increased in the last decades [2]. They can be found in a broad range of applications, such as electric vehicles (EV) [2], smart grids [3], aerospace applications [4] and all kind of small appliances applications as mobile devices [5]. Li-ion batteries are one of the most appealing batteries for high capacity ESS due to their high energy density, good temperature operation range, low selfdischarge and high cell voltage compared with NiCd or Pbacid [5].
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